Elastic fluid mechanism



. 061.29, 1946. R. BIRMANN ELASTIC FLUID MECHANISM 2 Sheets-Sheet 1Filed Dec. 13, 1941 ilk/7mm:

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Oct. 29, 1946. R. BIRMANN ELASTIC FLUID MECHANISM 2 Sheets-Sheet 2 FiledDec 15, 1941 yrzzwigm.

Mr/vfss PPM-- Patented Oct. 29, 1946 mesne assignments, to FederalReserve Bank of Philadelphia, a corporation of the United States ofAmerica Application December 13, 1941, Serial No. 422,837 7 6 Claims.

This invention relates to elastic fluid mechanisms, and moreparticularlyto the efficient cooling of elastic fluid turbines.

In my U. S. Patent 2,283,176, issued May 19, 1942, there are disclosedmethods and means for cooling elastic fluid turbines, particularly ofthe types operating at very high temperatures through the use ofproducts of combustion as driving fluid, this cooling being effectedwith at least no substantial loss of energy by imparting heat energy tothe cooling gases and then recovering a substantial part of such energyas either pressure of the exhausted gas or rotational effort 2 utilized,but the principle of boundary layer energization is alsoutilized tosecure aresulting torque in the direction of rotation of the turbinewheel by the lowering of pressure on the leading side of the turbineblades constituting the walls between the driving gas passages. As thecooling air mingles with the hot driving gas, it is further heated andupon discharge adds to the mass of the discharging jet to promote thedriving torque.

The various objects of the invention will become apparent from thefollowing description,

on the turbine Wheel. In the preferred mode of utilization of theinvention of said prior patent, the turbine gas passages and the coolinggas passages are separate and alternate about the turbine wheel. Thecooling gas passages, which in practice generally handle air, areprovided with impeller intake portions adapted to turn the gas flowradially outwardly and thereby effect substantial compression. Thisportion of the passage is then followed by a portion designed similarlyto a turbine bucket from which the gas is discharged rearwardly withrespect to the direc-] tion'of rotation. During the compression in theimpeller portion of the gas passage, the transfer of heat to the gas isdesirably at a minimum, though necessarily sometransfer occurs from thewalls of the passage. .A major portion of heat transfer occurs, however,near the completion of the compression and through the portion of thepassage joining the impeller and the turbine portions and in the latterportion.v The expansion of the compressed and heated gas causes thetransformation of both'the pressure and heat energy to a substantialextent into kinetic energy of the gas, which is discharged in the formof a I high velocity jet relative to the turbine-wheel.

Thus working torque is' applied to the wheel aiding the main drivinggases in effecting rotation of the shaft to carry the load. 7

The present invention involves the same basic principles as thoseoutlined above, but results in even more effective recovery of energyfrom the coolinggas. In accordance with the present invention, the gasis compressed in the impeller portions of passages alternating in aturbine wheel with the driving gas or bucket passages. At substantialcompletion of the compression, a major quantity of heat is applied tothe gases by transfer from the walls of the passages,;and the compressedgases are caused to discharge atsubstantial velocity as before. Thedischargehowe ever, is not in this case effected at substantially theaxial position of discharge from the driving gas passages, but ratherdirectly al the trailing walls of the driving gas passages substantiallyin advance, of their discharge ends. By this type of discharge, not onlyis the force of reaction read in conjunction With the accompanyingdrawings, in which:

Figure 1 is a diagrammatic sectional view illustrating a portion of aturbine wheel constructed in accordance with the present invention, the

View showing a circumferential projection of a section taken on asurface as indicated at I-l in Figure 3; 4

Figure 2 is va fragmentary'developed section taken on the surface ofrevolution the trace of which is indicated at 22 in Figure 1, theordinates of said Figure 2 being in terms of angles rather thancircumferential lengths;

Figure 3' is a section similar to Figure 2, but

taken on the surface of revolution the trace of I which is indicated at3-3 inFigure 1;

Figure 4 is a fragmentarysectional View showing the mode of applicationof the invention to a turbine having inserted blades, the sectionthrough the blade being taken on the radial surface the trace of whichis indicated at'4-4 in Figure 5; and g Figure 5 is a fragmentarydeveloped sectional view taken on the cylinder the trace of which isindicated at 5-5 in Figure 4.

Referring first tothe modification of Figures 1, 2 and 3, the turbinewheel indicated'therein is of the same general type as described indetail in said prior patent, and reference may be made theretoforthefundamental principles of design and theassociated parts involved inincorporation of this wheel in a complete mechanism. Thehub of the wheelis indicated at 2, and the blading is integral therewith in order toenable it to withstand the combination of high temperatures and intensecentrifugal forces. The turbine bladingis indicated at '4 and providesdriving gas passagesli, the form of which will preliminary compressionstages. This cooling gas is then subjected to deflection toward a radialdirection of flow with consequent additional compression finallyreaching a region of l maximum compression in the portions of theturbine blades directly between the iving gas passages. This region ofeach passage 8 opens adjacent the trailing face of the driving gas pas.-sage in advance of it through a radially elongated slot IE3 shaped inaccordance with known principles of nozzle design to form a nozzlearranged to accelerate the compressed coolinggas which will have beenheated to a quite considerable extent in the upper portion of thepassage, the major heating occurring after compression issubstantiallycompleted. The arrangement is such through the proper design of theparts, taking into account any preliminary compression of the coolinggas and the amount of heat added by conduction from the walls, to impartto the gas issuing from the nozzle slots iii a velocity substantially inexcess of the driving gas velocity at the point of communication betweenthe nozzle iii and the driving gas. The discharge is effected in adirection, for example, as indicated, slightly inwardly toward the axis,corresponding to the direction of flow of the driving gas at thelocation of the nozzle slot. Desirably, the center line of each of thecooling gas passages is at a distance from the axis of rotation in anintermediate portion thereof at least as great as at its intake anddischarge portions. Usually since discharge desirably takes place with aradial inward component, the intermediate portion of this axis will beat a greater radius than its discharge portion, as is the case inFigure 1. The net result of this is to provide not only a high reactionforce but also on the advancing side of each turbine vane a boundarylayer having a velocity substantially exceeding the velocity on thetrailing side of each turbine vane. This, in accordance with well-knownprinciples of aerodynamics, results in a net pressure difference acrosseach vane tending to provide a driving torque. It will be noted thatthis boundary layer is providedat .the radially outermost portions ofthe wheel so that the torque for a given pressure difference is amaximum. Furthermore, as this boundary layer flows, in a sheet over thevane, it will tend to accelerate the driving gases and will havevfurther heat. imparted to it so that this acceleration ta es place whileits own velocity decreases, the net result being a substantial averageincrease of kinetic energy of the gases discharged from the drivin gaspassages as compared with the kinetic energy which would result from theuse of the driving gases alone. In this way, there is recov-.

ered a net energywhich, in a carefully designed wheel, may substantiallyexceed the ener y put into the cooling gas during its compression byreason of utilization as mechanical .e ergy of a substantial portion ofthe heat transferred to-the cooling gas, The energy. recovery throughthe utilization of this energized boundary layer is somewhat greaterthan is attainable in accordance with the specific disclosure of saidprior patent. To secure maximum efficiency, the design of the passagesmay follow substantially the disclosure of saidprior patent modifiedslightly to provide the intermingling of the cooling and driving gasesas described. In' other words, the impeller passages and driving gaspassages are designed as described therein,the vanes present- 7 notparticularly critical 4 ing substantially air foil shapes to the flow ofboth cooling and driving gases.

Besides the advantages just indicated, there are others over theconstructions described in said prior patent. The long passages forcooling air extending to the discharge ends of the drivin gas passagesare eliminated, thus substantially reducingmanufacturing dimcultieswhich must be concentrated largely on securing proper discharge portionsof the cooling gas passages. The inlet portions of the cooling gaspassages are as to design, provided their pick-up angles are correct andprovision is made for smooth flow. Even if the coolin air passages ofthe type described in said prior patent are made as narrow as possiblefrom a manufacturing point of view, the thickness of the working bladesbetween the driving gas passages becomes excessive when the coolingpassages are extended to the discharge face of the wheel. This excessivethickness results in the necessity for substantial departure from thebest airfoil sections and particularly results in a serious reduction incapacity of thewheel due to the fact that so much discharge area must besacrificed for the cooling air passages and wall thickness. In thepresent arrangement, however, the sheet of cooling air can be made asthin as de sired and, in fact, a very high velocity of flow consistentwith this is desirable. No boundary wall is necessary, and, therefore, adischarge area is attainable.

The high velocities of the cooling air are not only desirable forproducing a maximum torque as described above, both by reaction and byreduction of pressure on the trailing walls of the turbine buckets, butprovide also ideal conditions for the cooling of the blading, since therate of heat transfer from a metal surface to a gas flow ing over itincreases with the velocity of the gas. At the same time, the relativevelocity between the cooling air and driving gas is relatively low sothat there is comparatively little heat exchange between the tworesulting in the maintenanceof high cooling ability of the cooling air.The improved arrangement accordingly offers numerous advantages, allconsistent with each other for the production of maximum efficiency.

The invention is not soleiy applicable to the type of wheel described inFigures 1, Z and 3, but is also applicable to the type of wheel havinginserted blades, which is ,quite practical for lower temperature andlower speed operation. Figures i and 5 show the application of theprinciples of theinvention to such type of mechanism.

The turbine wheel in this embodiment of the invention is indicated at 12carried by a hollow shaft l4 designed to provide for the flow-of coolingair through passages it to the blading, compression taking place inpassages 55 which function as impeller passages. The periphery of thewheel is designed, as indicatedat it, to carry the blades l8, which areformed integral with blocks 20 suitably interengaged with the disc. The

' blades i8 may have generallyconventional-shape,

stantially in advance of the discharge ends of the buckets, therebyproviding a boundary layer of the cooling gas moving at a highervelocity than the driving gas passing through the driving gas passages,to produce a resulting pressure difference across each blade H8 in thesame fashion as described in connection with the previous modification.

It will be evident that the invention may be embodied in turbinesgenerally, in forms other than those specifically indicated.

What I claim and desire to protect by Letters Patent is:

1. An elastic fluid mechanism including a re. tor mounted for rotationabout an axis and'provided with turbine passages, means for directinghot driving fluid into the turbine passages, and passages for elasticcooling fluid adjacent to said turbine passages, each of said elasticcooling fluid passages opening, through a nozzle constructed vided withturbine passages, means for directing hot driving fluid into the turbinepassages, and passages for elastic cooling fluid adjacent to saidturbine passages, each of said elastic cooling fluid passages opening,through a nozzle constructed and arranged to expand the cooling fluidand impart to it a high velocity at least of the order of magnitude ofthe velocity of the driving fluid through the turbine passages, adjacentto the trailing wall of a turbine passage to discharge the cooling fluidat such high velocity along said wall in the direction of flow ofdriving fluid, and

each of said cooling fluid passages having a portion through which flowtakes place with a radially outward component of motion to effectcompression of the cooling fluid prior to its discharge.

3. An elastic fluid mechanism including a rotor mounted for rotationabout an axis and provided with passages for elastic fluid havingaxially spaced intake and discharge portions and continuous between saidportions, said passages extending spirally in the rotor substantiallyabout its axis, as viewed in a radial direction, from their intakeportions to their discharge portions, and the center line of each ofsuch passages being at a distance from the axis of rotation in anintermediate portion thereof at least as great as at its intake anddischarge portions, the passages being constructed and arranged so thatcompression occurs in the intake portions thereof, said rotor also beingprovided with turbine buckets, and means for directing hot elastic.driving fluid to the turbine buckets to effect driving of the rotor andsubstantial heat transfer to elastic fluid during its flow through saidpassages, said pas-' sages and turbine buckets being so constructed andarranged that the turbine buckets are closely adjacent to only thoseportions of each passage beyond its intake portion in which nosubstantial compression occurs so that the transfer of substantialamounts of heat is confined to such portions in which no substantialcompression occurs, and each of such passages being constructed andarranged as a nozzle at its discharge portion to effect thereinexpansion of the fluid and to discharge it at high velocity backwardlyrelatively to the rotor along the trailing wall of an adjacent bucketand in the direction of flow of driving fluid through the bucket so thatpower is imparted thereby to the rotor both by reaction and by reductionof pressure on said bucket wall.

4. An elastic fluid mechanism including a rotor mounted for rotationabout an axis, passages for driving fluid in the rotor, and means fordirecting hot driving fluid to said passages, said rotor being providedwith passages for elastic cooling fluid having axially spaced intake anddischarge portions and continuous between said'portions, said passagesextending spirally in the rotor substantially about its axis, as viewedin a radial direction, from their intake portions to their dischargeportions, each passage extending at its intake portion in the directionof approach of cooling fluid to the rotor to scoop up and compress thecooling fluid and imp-art to it an axial component of fl'ow, and each ofsuch passages being arranged as a nozzle at its discharge portion todischarge the cooling fluid rearwardly at high velocity along thetrailing wall of an adjacent driving fluid passage and in the directionof flow of driving fluid, said driving fluid passages and cooling fluidpassages being so constructed and arranged with closely adjacentportions that compressed cooling fluid receives from the rotor in thecooling fluid passages beyond said intake portions heat from the drivingfluid.

5. An elastic fluid mechanism including a rotor mounted for rotationabout an axis, turbine passages in said rotor, means for directing hotdriving fluid into the turbine passages, and passages located adjacentthe turbine passages for elastic cooling fluid having axially spacedintake and discharge portions and continuous between said portions, saidpassages extending spirally in the rotor substantially about its axis,as viewed in a radial direction, from their intake portions to theirdischarge portions, each passage extending of cooling fluid to the rotorto' scoop up and at its intake portion in the direction of approachcompress the cooling fluid and impart to it an axial component of flow,and each of such pas- I sages being arranged as a nozzle at itsdischarge portion to discharge the cooling fluid rearwardly at highvelocity along the trailing wall of an adjacent turbine passage and inthe direction of flow of driving fluid, said turbine passages andcooling fluid passages being so constructed and arranged with closelyadjacent portions that compressed cooling fluid receives from the rotorin the cooling fluid passages beyond said intake portions heat from thedriving fluid.

6. An elastic fluid mechanism including a rotor mounted for rotationabout an axis and provided with turbine passages, means for directinghot driving fluid into the turbine passages, and passages for elasticcooling fluid adjacent to said turbine passages, each of said elasticcooling fluid passages opening adjacent to the trailing wall of aturbine passage and constructed and arranged as a nozzle to dischargethe cooling fluid at high velocity, at least of the order of magnitudeof the velocity of the driving fluid through the turbine passages, alongsaid wall in the direction of flow of driving fluid, and each of saidcooling fluid passages having a portion through which flow takes placewith a radially outward component of motion to effect compression of thecooling fluid prior to its discharge.

RUDOLPH BIRMAN N.

